Electric arc light source and method



Nov.425, 1969 D. G. VAN oRNuM 3,480,829

`ELFCTRI ARC LIGHT 4SOURCE AND METHOD Filed March 8, 1965 2 Sheets-Sheet1 Nov. 25, 1969 D G, VAN ORNUM 3,480,829

ELEC'IRIC ARC LIGHT SOURCE AND METHOD Filed March 8, 1965 2 Sheets-Sheet2 FIGJ 'MW rroR/vfys' United States Patent O 3,480,829 ELECTRIC ARCLIGHT SOURCE AND METHCD Delbert G. Van Ornum, Newport Beach, Calif.,assignox' to Geotel Inc., a corporation of Delaware Filed Mar. 8, 1965,Ser. No. 437,963 Int. Cl. H01j 7/24; H05b 31/26 U.S. Cl. 315-111 17Claims ABSTRACT F THE DISCLOSURE A vortex-stabilized radiation sourcewherein one of the electrodes has a recess therein, the recess having agenerally radial bottom wall which forms the arcing surface of therecessed electrode. Means are provided to drain gas from the peripheralregion of the recess.

tion by axial gas flow, and to other forms of stabilization. t

In order to provide a satisfactory radiation source, a major portion ofthe vortically-flowing gas must discharge from the arc chamber throughan outlet located adjacent the arc (electrical discharge) and alsolocated at or near the axis of the chamber. Another requirement is thatthe light generated by the arc must be transmitted therefrom through atleast a portion of the `wall of the chamber, as distinguished from:being transmitted through the gas-outlet opening. Relative to thelatter factor, it has been found that the emission of light from thedecaying plasma produced by electric arcs (not from the electric arcsthemselves) is inefficient.

In discharging the vortically-flowing gas from the arc chamber, at aregion adjacent the arc and also adjacent the axis of the chamber, itwas for a number of years thought to be optimum to effect such gasdischarge through a single outlet opening which is coaxial with thechamber axis. Such a radiation source produced major benefits whencompared to the prior art. Thus, for example, theefciency oftransmission of light from each exposed section of the arc was markedlysuperior to the transmission efficiency relative to arcs stabilized byaxially-ilowing gas. On the other hand, it was found that a largeportion of the arc itself extended into the axial discharge conduit, sothat radiation from such arc portion in the conduit was largelyobscured. This factor, in combination with factors such as the increasedvoltage required by the long arc (and because of the fact that the gasflowed rapidly adjacent the footpoint of the arm), rendered the over-allefficiency of such vortex-stabilized radiation source relatively low.

A further important characteristic of vortex-stabilized radiationsources, of the above-indicated type wherein the gas exhausts through asingle axial outlet opening, is that two strong light-emission zones arein evidenceone adjacent the cathode and the other extending into theoutlet opening in the anode (the outlet opening being normally providedin the anode). The presence of two such emission zones is very diierentfrom the usual short arc lamp, for example, because in such lamps theonly strong emission zone is adjacent the cathode. The indicated strongor hot emission zone within the anode opening transmits Patented Nov.25, 1969 large amounts of heat energy to the anode, by conduction,radiation and electron collisions. Such large amounts of heat aredetrimental to anode life, as Well as being detrimental to radiativeefficiency.

Although the above-indicated vortex-stabilized radiation sources, of thesingle axial-outlet type, have for years been regarded as optimum, theyhave recently been very substantially improved upon. Thus, in co-pendingpatent application Ser. No. 421,370, led Dec. 28, 1964, for an Apparatusand Method for Generating Light, inventors John W. Winzeler and -DelbertG. Van Ornum, a radiation source is described wherein the arc isrelatively short and the voltage requirement greatly reduced so that amuch improved etiiciency results. Furthermore, such source ischaracterized by important advantages relative to emissioncharacteristics, and relative to gas pressuredrop characteristics atvarying power levels. However, such source is also subject to certaindisadvantages, one of which is that etiicient operation may not besustained at very high power levels.

It is, therefore, a primary object of the present inveni tion to providean apparatus and method for generating light, which apparatus and methodeliminate various disadvantages relating to the above-specified andother, radiatlon sources.

A further object is to provide an apparatus and method for generatinglight in a manner characterized by high efficiency, extremely longelectrode life at high power levels, controllability of the emissioncharacteristics of the arc, controllability of the shape of the arc, andother important advantages.

A further object is to provide a radiation-source apparatus and methodcharacterized by a relatively small anode fall voltage, whereby a highcurrent may be achieved at relatively low voltage so that the radiationeiiiciency increases markedly.

A further object is to provide a double-walled light source havingimproved gas-inlet means.

A further object is to provide a light-source apparatus and methodwherein only a small portion of the gas flowing through the exhaustoutlets is directly heated by the arc, thereby achieving advantagesincluding long electrode life.

These and other objects will become apparent from the following detaileddescription taken in connection with the accompanying drawings in which:

FIGURE 1 is a view, primarily in longitudinal section, of a radiationsource constructed in accordance with the present invention;

FIGURE 2 is a fragmentary transverse sectional view on line 2--2 ofFIGURE 1;

FIGURE 3 is a section on line 3--3 of FIGURE 2;

FIGURE 4 is an enlarged view of the central portion of the showing ofFIGURE 1;

FIGURE 5 is a transverse section on line 5 5 of FIG- URE 4.;

FIGURE 5a is a section on line Sa-Sa of FIGURE 4;

FIGURE 6 is a fragmentary view, corresponding to the left portion ofFIGURE 4 but showing a modied form of the invention;

FIGURE 7 is a sectional View along line 7--7 of FIG- URE 4; and

FIGURE 8 is a fragmentary sectional view on line r 8-8 of FIGURE 7.

Referring first to FIGURE 1, the illustrated apparatus comprises firstand second metal body elements 10K and 11 comprising flanges 12 and 13on stems 14 and 15, respectively. Extended between the flanges 12 and 13is a relatively large-diameter tubular outer envelope 16 which may beformed of quartz, fused silica, or other suitable transparent material.Extended between the opposed inner end portions of the stems 14 and 15,in coaxial relationship relative to outer envelope 16, is a tubularinner envelope 17 which may be formed of the same material. Envelopes 16and 17 define between them an annular outer chamber 18 into which gas isintroduced as will be indicated subsequently, such chamber =beingmaintained sealed from the chamber defined within inner envelope 17 bysuitable O-rings 19 or other seals. The chamber defined within envelope17, between the opposed inner ends of stems 14 and 15, is the arcchamber and has been given the reference number 20.

Proceeding next to a preliminary description of Athe stem 14, thecylindrical main body of such stem (which is coaxial with both chambers18 and 20) is provided with a central chamber or bore indicated at 22.The inner end of the stem, radially outwardly of bore 22, is shapedexteriorly as a frustoconical surface 23, such surface being one of theend surfaces of the anode element of the present construction. Thefrustoconical surface 23 is shown as merging with a radial surface 24which lies in a plane perpendicular to the common axis of chambers 18and 20. The remaining and highly important components of the anode(formed by the inner end of stem 14, and by associated parts) will bedescribed hereinafter, after a description of the associated cathode,power means, gas-flow means and cooling means.

The stem 15, which normally forms the cathode of the apparatus, may beshaped with the illustrated conical inner end portion 26 which iscoaxial with the common axis of chambers 18 and 20. The base of theconical exterior surface of end 26 merges with a radial surface 27 whichis perpendicular to such common axis. The region radially-outwardly ofthe base of cone 26 receives relatively cool gas which is deliveredthereto through passages or conduits 28, such passages being oriented(as will be described) to effect a strong vortical flow of gas in arcchamber 20 about the axis thereof. Gas enters the passages 28 from anannular groove 29 which is formed in stem adjacent one end of envelope17.

The gas-inlet passages 28 to arc chamber 20 are best shown in FIGURES 4,7, and 8. Such passages extend in a direction toward the interiorsurface of inner envelope 17, so that the inflowing gas will cool andclean such envelope. Thus, the ends (inner) of passages 28 whichdirectly communicate with chamber are shown as being located adjacentthe junction of surface 27 with the conical surface of element 26. Theremaining (outer) ends of the passages, which communicate with annulargroove 29, are disposed closer to the axis of the apparatus, so that theabove-indicated direction of gas flow toward envelope 17 results.

As best shown in FIGURE 8, the passages 28 not only extend towardenvelope 17 but, much more importantly, extend in a direction which isgenerally tangential to the axis of chamber 20, so that the necessaryvortical or helical gas flow is achieved. Preferably, a substantialnumber of inlet passages 28 are provided, four such passages beingillustrated in FIGURE 7. Passages 28 are identical to each other, andare spaced 90 degrees apart.

Each of the passages 28 is inclined at an acute angle (shown as 45degrees, FIGURE 8) to a plane containing the axis of the light source,in such relationship that the gas flow in chamber 20 will be smoothlyhelical in nature. This produces benefits including increasing arcstability, and decreasing the gas pressure drop through chamber 20.

The gas which is delivered to the annular groove 29, and thus lthroughpassages 28 to arc chamber 20, is supplied to annulus 18 (FIGURE 1)through one or more inlet passages indicated at 31 in FIGURES 1-3.Passage 31 is oriented in such manner as to effect a helical flow of gasin the annulus 18 between envelopes 16 and 17, the gas spiralinglongitudinally along envelope 18 and then entering the annular groove29. Such spiral flow is highly beneficial in uniformly cooling all partsof both envelopes.

Gas is supplied to the inlet passage or passages 31 through arecirculation conduit 32 in which are interposed a suitable pump 33 andheat exchanger 34. The heat exchanger 34 effects cooling of gas whichdischarges from arc chamber 20 through the anode, by means of passagesand conduits to be described hereinafter.

The cathode 26 is water cooled in a suitable manner. For example, asshown in FIGURES 1 and 4, the stem 15 may be formed with a longitudinalpassage or opening 36 into which is inserted a water-inlet conduit 37.Water introduced through conduit 37 impinges against the apex portion ofthe cathode cone 26, and then flows outwardly (radially around conduit37) for discharge through an outlet 38.

A suitable current source 39, preferably adapted to deliver a very highcurrent, is connected between the elements 10 and 11 (which are formedof copper or other highly conductive material) by means of leads 41 and42. A starter circuit, indicated schematically at 43, may be interposedin one of the leads (for example, number 42) in order to initiate thedischarge between the electrodes. The starter circuit may include meansto create a momentary high-voltage or high-frequency pulse discharge.

The current sou-rce 39 should be a D.C. source having the positiveterminal thereof connected to element 10, so that the inner end of stem14 serves as the anode as previously indicated. yIt is to be understood,however, that reverse polarity may be employed if desired. It is also tobe understood that various other current sources, for example A.C.sources, pulse sources, etc., may be ernployed if desired.

DETAILED DESCRIPTION OF THE ANODE ASSEMBLY Stated generally, the anodeis pr-ovided with a recess or opening 45 which is coaxial with the arcchamber 20, the bottom of the recess (rat least in the vicinity of theaxis of arc chamber 20) being closed.

Stated more definitely, the recess 45 has an annular wall 47, shown asbeing cylindrical about the axis of arc chamber 20. The bottom of recess45 is shown as comprising a wall 48 lying generally in a radial plane(generally perpendicular to the axis of the arc chamber). The centralregion of wall 48 may protrude somewhat in a direction toward thecathode. Recess 45 may be termed the foot chamber or opening, becausethe arc seats or foots therein.

The diameter of the wall 47 should be substantially greater than thediameter of the arc 49 which is generated along the axis of chamber 20,it being understood that the arc diameter (in chamber 20) varies inaccordance with power level, gas-flow conditions, gas pressure, etc. Thediameter of wall 47 is another factor (as will be described relative toFIGURE 6) operating in a very substantial manner to determine thediameter of the major portion of arc 49, namely the arc portion which isfully exposed within chamber 20.

For maximum-efficiency operation, the diameter of the portion of annularwall 47 closest to cathode 26 should not be substantially smaller thanthe axial distance from wall 48 to surface 24. Such portion of wall 47defines an opening through which recess 45 communicates with arc chamber20.

To state the above in another manner, the bottom wall 48 of the recess45 should, for highest-efficiency operation, be suiciently close to thearc chamber 20, namely to the radial surface 24 in the illustratedconfiguration, that light emanating from the center of wall 48 (at theaxis of the arc chamber) will be transmitted in a generally radialdirection (as well as an axial direction) as indicated by the phantomlines V51 in FIGURE 4. The ratio of the diameter of recess 45 to thedepth thereof may be termed the aspect ratio, and may be varied as willbe described hereinafter relative to FIGURE 6.

The gas-discharge passages 46 are shown as communicating with the recess45 at the periphery of the arcing wall 48. Alternatively, oradditionally, passages 46 may communicate with recess 45 at regionscloser to radial surface 24 (spaced from wall 48). A plurality of suchgas-discharge passages should be provided, in spaced relationship aroundthe recess. Thus, in the illustrated form, three such passages orconduits 46 are shown. The three passages 46 have radially-extendingnozzle portions 52- 54 (FIGURE 5a) which intersect the wall 47 of therecess 45. Such nozzle portions 52-54 (forming the intake ends ofpassages 46) communicate with the main portions rof passages 46, thelatter extending in inclined manner through a cooling (heat transfer)section of the anode as will be described hereinafter.

In all cases, the distance between surface 24 and intake means 52-54 isshort, and should be less than the diameter of the portion of wall 47closest to the cathode 26.

The described provision of an arcing electrode portion 48 through whichgas does not discharge, in combination with the peripherally-located gasdischarge means 52-54, and further in combination with the -annularelement 47, provide major advantages relative to such factors as powercapability, efliciency, emission characteristics, electrode life, etc.It is emphasized, however, that a substantial factor relative to thepresent light source and method relates to the manner of cooling thewalls of recess 45 to provide a heat-sink action which combines with thepressure-sink action effected by passages 46.

Proceeding next to a description of the cooling means, and to a furtherdescription of the gas-discharge means, the stem 14 of the anode isprovided with a solid, reentrant portion 56 having a cylindricalperipheral wall 157 coaxial with the axis of the stern 14 and of thechamber 22 therein. The base of re-entrant portion 56, that is to saythe inner end of the chamber 22, is located in spaced relationship fromanode surfaces 23 and 24, generally radially-outwardly of the bottomwall 48 of recess 45. There are thus formed large cross-sections throughwhich heat may be transferred from the walls of recess 45 to the innerend of chamber 22.

A metal tube 58 is connected to (or integral with, as shown) the end ofre-entrant portion 56, and extends axially of chamber 22 for connectionto the conduit 32 through which the gas recirculates. Each of thegas-outlet passages 46 communicates with the passage formed in tube 58.

A water-separator tube or conduit 59, having a diameter substantiallylarger than that of tube 58, extends into the chamber 22 into telescopedrelationship with reentrant portion 56. The inner diameter of the waterseparator tube is slightly larger than the diameter of wall 57, so thatan annular gap 61 is provided as shown in FIG- URE 4 (such gap being sosmall `as to prevent illustration thereof in FIGURE l).

The annulus `62 between tubes 58 and 59 communicates with a plurality ofangularly-Shaped coolant passages 63- 65 having corner or elbow portionsdisposed adjacent the arcing bottom wall 48 of recess 45. Such passages63-65 not only have inlet ends communicating with annulus 62 but alsohave outlet ends communicating with chamber 22 radially-outwardly ofwater-separator tube 59.

Water is introduced into the annulus 62 by means of an inlet conduit y66(FIGURE l), and flows to the right through such annulus (FIGURES l and4) to effect a certain amount of cooling of the gas which passesoutwardly through tube 58. Upon reaching -the inner end of annulus `62,the water separates, one portion flowing through the annular gap `r61(FIGURE 4) and the other portion flowing through the elbow-shapedpassages 63-65. The water then flows to the left, through the annuluswhich is defined radially-outwardly of water separator 59 and within thechamber 22, for discharge through an outlet conduit 67.

In the described manner, relatively cool water is deli-vered to theregion surrounding the 4base of re-entrant anode portion 56, and is alsodelivered. directly (through passages 63-65, FIGURE 5) to the regionadjacent the arcing wall 48 of the anode. This effects an extremelyeflicient cooling of all wall portions of recess 45. In addition, thewalls of the gas-discharge passages 46 are effectively and eicientlycooled. In the latter connection it is pointed out that the number ofgas-discharge passages 46 is preferably equal to the number of waterpassages 63-65, and that such passages are offset (as shown in FIGURE 5)so that one gas passage lies between each two adjacent water passages.The amount of heat transfer from the gas-discharge passages to the wateris thus comparable to the heat transfer from the walls of recess 45 tothe water.

DESCRIPTION OF THE METHOD, AND OF VARIOUS CRITICAL RELATIONSHIPS Statedgener-ally, the method of the invention comprises eifecting gas vortexstabilization of a high-current electric arc in a chamber, causing atleast one footpoint of the arc to extend into an opening in .at leastone of the electrode assemblies between which the arc is maintained,effecting footing of the arc in the opening, discharging gas from theopening through conduit means communicating therewith and having anintake portion located near the chamber, and transmitting light fromsuch arc through a window in the wall of the chamber. The method furthercomprises cooling the wall portions of the opening or recess in order toprovide a heat-sink action which c0- operates with the pressure-sinkaction caused by the outlet-conduit means. Such heat-sink andpressure-sink actions augument the vortex stabilization effect, andfacilitate footing of the arc.

Stated in another manner, the method of the invention comprisesproviding an arc chamber having a wall which is a surface of revolutionabout a central axis, -maintaining a high-current electric arc alongsuch axis between spaced electrodes, causing one end portion of such arcto extend into a recess which is defined by a wall coaxial with andspaced outwardly from such axis, footing the arc on the bottom wall ofthe recess, elfecting generally tangential introduction of gas into aperipheral region of the arc chamber, preventing discharge of gas Vfromthe recess along such axis, discharging gas from the recess throughpassage means which communicate with the recess at least one regiondisposed radially-outwardly from the axis, and transmitting light fromthe arc through the surface of revolution.

It is pointed out that the gas discharges vfrom arc chamber 20 (notrecess 45) through an axial opening l(namely, recess 45) in one of theelectrodes (the anode). However, such axial opening is relatively largein diameter and, furthermore, is not a continuous straight conduit butinstead has a bottom arcing wall 48 which prevents discharge of gas-along the exact axis of the recess. Thus, the arc does not extend intothe gas-discharge passages 46 but instead foots on the wall 48.Furthermore, and very importantly, the arc spreads after entering therecess 45 to provide a generally conical footing region 68 (FIGURE 4)which merges with the generally cylindrical main body of the arc 49.Such spreading of the arc over the majority of the area of arcing wall48 reduces current density at the electrode, greatly increases electrodelife, and changes the emission characteristics of the arc as will beindicated hereinafter.

The gas discharges from the chamber 20 at a region adjacent the |arc andalso relatively adjacent the axis of the arc chamber, as is required forefficient vor-tex action in a radiation source. However, the gas doesnot discharge from the recess 45 along the axis thereof but instead inthe generally radially-outward direction through the portions 52-54 ofthe gas-discharge passages 46. Because of the lfact that the arc doesnot extend into such passages, and because of the efiicient watercooling of such passages as described above, there is only a very smallamount of erosion of the passage walls.

The annular wall 47 of the recess or opening, although relatively largein comparison with prior-art constructions of the type wherein the gasdischarges through a long axial passage or conduit, has been found toproduce a surprising -degree of arc stabilization and constriction. Asindicated above, the diameter of wall 47 is caused to be suicientlylarge to permit eicient transmission of light from arcing surface 48,and sufciently large that the electrode will not melt or erodeexcessive-ly at surface 47, but sufficiently small to effect the desireddegree of constriction and stabilization of the arc 49. Because the wall47 is located radially-outwardly from -a portion of the arc, thediameter of the wall 47 has a much greater bearing on the diameter ofarc 49 than would be the case if the wall 47 were spaced -axially fromthe arc. Thus, for example, the indicated arc 49 (within chamber 20) hasa diameter substantially smaller than would be the case if a cylindricalarcing member were connected axially to surface 48 and extended out ofrecess 4S into chamber 20 (there then being no arc portion -within therecess).

The intake ends 52-54 of passages 46 are sufficiently close to the arcto effect an efficient draining olf of the layer of partially-excitedgas between the arc 49 and the relatively cool, vortically-flowing gassurrounding the arc. As described in co-pending patent application suchas the one cited above, such draining off of the partiallyexcited gasincreases the eciency of transmission of ultraviolet radiation from thehot core of the arc through the window or envelope 17.

Because there is no subst-antial axial gas-outlet opening in arcing wall48, the gas present within the hot core of the arc 49 is rel-ativelystagnant. Such gas being relatively stagnant, it may be maintained in anextremely hot, highly-excited condition with a minimum of energy. Statedin another manner, observation of the arc indicates that only a smallportion of the gas moving through the exhaust holes 52-54 is directlyarc heated, most of the exhaust gas coming instead from thepartially-excited gas around the arc column 49. The result is asignificant increase in the efficiency of the radiation source.

It is emphasized that, for a given pressure in the main body of arcchamber 20, the pressure at the axis of such chamber is substantiallyhigher in the present source than in constructions wherein the gasdischarge is through a straight passage along the axis. Statedotherwise, the gas pressure along the axis of chamber 20 is maintainedrelatively high because the gas is relatively stagnant at such axis,instead of being continuously drained. The resulting high pressure alongthe axis is distinctly desirable relative to such factors as radiationcharacteristics and efhciency.

A further important result of the relatively stagnant gas which ispresent within the arc core 49 is that there is an extremely conductivepath between wall 4S and the arcing apex of cathode 26. Such conductivepath, the relatively stagnant hot gas within the base portion 68 of thearc, the large area of arcing portion 48 of the anode, and otherfactors, operate to cause the voltage drop between anode and cathode tobe low in comparison to prior-art structures, Thus, for a given powerinput, the current is relatively high and the voltage relatively low.Because light emission depends largely upon current as distinguishedfrom voltage, the luminous efliciency of the present light source isextremely high.

As previously indicated, the emission of radiation from the arc portions49 and 68 (FIGURE 4) is substantially different than in variousprior-art devices. For example, the microspectral radiancy of thepresent recessed-plate vortex-stalibized arc shows remarkable axialuniformity in the infrared. Relative to ultraviolet radiation, there isa high emission zone adjacent the cathode 26, the remainder of the arcbeing substantially uniform relative to lightemission characteristics.There is no hot emission zone in evidence near the anode, the arcinstead increasing in width within the anode recess and contacting thesurface 48 over a large area, as stated above.

By changing the diameter of wall 47, and the depth of recess 45, theemission characteristics of the arc may be substantially altered.Furthermore, the physical shape of the arc (including the conical base68 thereof) may be changed in various desired manners and in accordancewith the requirements of the optical system with which the light sourceis employed. Referring to FIGURE 6, there is shown an anode constructionwherein the recess 45a is smaller in diameter and greater in depth thanin the anode construction shown in FIGURE 4. The light emitted from therecess, as indicated by the phantom lines 51a, then extends through asmaller angle than in the embodiment of FIGURE 4. However, thecylindrical portion 49a of the arc is smaller in diameter (all otherconditions being equal) than in the embodiment of FIGURE 4, and theconical base 68a of the arc is also smaller in diameter.

In the described manner, the aspect ratio of the emitted light, thespectral distribution throughout the arc, the emission intensity ofvarious portions of the arc, and other factors, may be altered oradjusted in numerous desired ways.

As previously indicated, the power capabilities of the present lightsource are vastly superior than in the case of prior-art light sourcesof the same general class. For example, the present power source willoperate for many hours without substantial deterioration or wear of theelectrodes, and at power levels much higher than in the case of thelight source described in the above-cited patent application.

The gas employed in the present radiation source should be a noble gassuch as (for example) argon, neon, krypton, xenon, or mixtures thereof,at high pressures. The gas pressure within arc chamber 20 should be onthe order of hundreds of pounds per square inch.

It has been found that maximum stability of the arc is achieved when thediameter of the cylindrical body of the arc (in chamber 20) is in therange of about one-third to two-thirds of the diameter of the portion ofwall 47 nearest the cathode 26. The diameter of such cylindrical portionof the arc should not be as large as that of wall 47, because flow ofcold vortex gas into the recess would then be impeded.

It is pointed out that the cathode 26 of the present source is (like theanode) devoid of gas-outlet passages along the axis of the arc chamber.Thus, the stagnant gas condi- Specific example As a specific example ofone operative form of the present source, which example is given by wayof illustration and not limitation, the diameter of the cylindrical wallof the recess 45 may be 5 mm., and the depth of the recess (betweensurface 24 and surface 48) may be 2.5 mm. The diameter of each gasconduit portion 52-54 may be 1.5 mm., whereas the diameters of the fourgas-inlet conduits 28 may be 0.6 mm. The diameter of the chamber 20 maybe 25.0 mm., the spacing between the apex of cathode cone 26 and surface48 being 11.5 mm.

The arc current may be 150 amperes, and the voltage between theelectrodes volts. The gas employed may be argon, at a pressure of 14atmospheres within arc chamber 20.

The resulting arc had a diameter of 2.0 mm. along the cylindricalportion 49 thereof. The luminous efficiency of the arc was 17 lumens perwatt, this being very much better than a typical vortex arc with astraight axial eX- haust orifice.

The foregoing detailed description is to be clearly understood as givenby way of illustration and example only, the spirit and scope of thisinvention being limited solely by the appended claims.

I claim:

1. A method of eifecting gas vortex stabilization of a high-currentelectric arc in a chamber, which comprises:

maintaining a high-current electric arc between first and secondelectrodes and along a predetermined axis in an are chamber,

causing atleast one footpoint of said arc to extend into a recess in atleast one of said electrodes,

effecting footing of said arc at the center of said recess,

effecting vortical ow of gas about said axis in said chamber,

discharging gas from said recess through conduit means locatedradially-outwardly from said arc, and transmitting light from said arcthrough a window in the wall of said chamber.

2. The invention as claimed in claim 1, in which said method furthercomprises cooling the walls defining said recess.

3i. A method of effecting gas vortex stabilization of a high-currentelectric arc in a chamber, which comprises:

maintaining a high-current electric arc in an arc chamber along an axisbetween spaced electrodes therein,

causing one end portion of said arc to extend into a recess having aside wall coaxial with and spaced outwardly from said axis,

footing said arc on the bottom wall of said recess,

effecting generally tangential introduction of gas into a peripheralregion of said arc chamber,

preventing discharge of said gas from said recess along said axis,

discharging said gas from said recess through passage means whichcommunicate with said recess at at least one region disposedradially-outwardly from said axis, and

transmitting light from said arc through a light-transmissive window inthe wall of said chamber.

4. A method of generating high-intensity light, which comprises:

footing one end of an electric arc on the bottom wall of a shallowrecess in a metal electrode, footing the other end of said electric arcon a second electrode spaced from said first-mentioned electrode,

passing a coolant through said first-mentioned electrode to`effectcooling of the side and bottom walls of said recess,

causing said arc to extend along an axis which is generallyperpendicular to said bottom wall and intersects the same in the centralportion thereof, continuously passing high-pressure gas around said arcand thence into said recess, continuously draining said gas from saidrecess adjacent the side wall thereof, and

transmitting to a desired area the light generated by said arc.

5. Apparatus for generating high-intensity light, which comprises:

wall means to define an arc chamber,

at least a portion -of said wall means being transparent,

wall means to define a foot chamber communicating through an openingwith said arc chamber,

means to form an arcing surface in said foot chamber in the regionopposite said opening and coaxial with said opening,

said arcing surface being sufficiently close to said opening, and saidopening being sufficiently large in diameter, that light generated in atleast the center of said arcing surface may be readily transmittedthrough said transparent wall means, an electrode having an arcingportion disposed in said arc chamber opposite said opening,

means to effect a high-current electrical discharge between said arcingsurface and said arcing portion of said electrode, means to introducegas into said arc chamber and to effect vortical ow of said gas about anaxis which extends from said arcing surface through said opening to saidarcing portion of said electrode, and means to drain said gas from saidarc chamber through said opening,

said drain means including gas-outlet means com municating with saidfoot chamber at the peripheral region thereof, said foot chamber definedby said second-mentioned wall means being located in an electrodeadditional to said first-mentioned electrode. 6. Apparatus forgenerating high-intensity light, which comprises:

wall means to define an arc chamber,

at least a portion of said wall means being transparent, at least amajor portion of said wall means comprising a surface of revolutionabout a central axls, wall means to define a foot chamber communicatingthrough an opening with said arc chamber,

said opening being defined by an annular Wall coaxial with said centralaxis, the diameter of said annular wall being much smaller than that ofsaid surface of revolution, means to form an arcing surface in said footchamber coaxially of said central axis and in the region of said footchamber opposite said opening,

said arcing surface being sufficiently close to said opening, and saidannular wall being sufficiently large in diameter, that light generatedat at least the portion of said arcing surface at said axis may bereadily transmitted through said transparent wall portion, said footchamber being formed in an electrode incorporating said annular wall andsaid arcing surface, a second electrode having an arcing portiondisposed in said arc chamber opposite said opening, means to maintain ahigh-current electric arc between said arcing surface of saidfirst-mentioned electrode and said arcing portion of said secondelectrode,

said means being a D.C. source having the positive terminal thereofconnected to said first mentioned electrode, and the negative terminalthereof connected to said second electrode, means to introduce gas athigh pressure into said arc chamber and to effect vortical ow of saidgas in said chamber about said central axis,

said gas-introduction means being independent of said foot chamber andof said. opening, means to discharge at least a portion of said gas fromsaid are chamber through said opening,

said discharge means including gas-outlet means communicating with saidfoot chamber,

said gas-outlet means including a plurality of passages the intakeportions of which communicate with said foot chamber adjacent saidannular wall, and means to pass coolant continuously through saidfirstmentioned electrode to thereby effect cooling of said arcingsurface and the walls of said passages. 7. Apparatus for generatinghigh-intensity light, which comprises:

light-transmissive wall means to dene an arc chamber, first and secondelectrodes having solid arcing portions disposed in spaced relaionshipin said chamber,

said arcing portions being disposed along a predetermined axis in saidchamber,

one of said arcing portions being in a recess in one of said electrodes,

means to effect vortical fiow of gas in said chamber and about saidaxis,

said last-named means including means to introduce gas continuously intosaid chamber, means to maintain an electric are along said axis betweensaid arcing portions, and means to discharge said gas from said chamberthrough outlet means the intake portion of which is located radiallyadjacent said one arcing portion and exteriorly of said arc.

8. The invention as claimed in claim 7, in which said last-named meanscomprises at least three outlet passages having intake ends which arelocated radially adjacent said one arcing portion and are peripherallyspaced therearound.

9. Apparatus which comprises:

wall means to define an arc chamber,

at least a portion of said wall means being transparent, said wall meansincluding a surface of revolution about a central axis, means to definea solid, hole-free arcing surface disposed on the axis of said surfaceof revolution,

means to introduce gas continuously into said chamber and to effectvortical flow of said gas about said axis in said chamber,

means to maintain an electric arc along said axis between said arcingsurface and an electrode space and insulated therefrom.

outlet means located adjacent the region encompassing said arcingsurface to continuously discharge said gas Ifrom said chamber, and

means to define an annular wall in said chamber caxially with said axisand between said arcing surface and said electrode,

said annular wall being sufficiently small in diameter to effectspreading of the portion of said arc extending between said arcingsurface and the part of said annular wall nearest said electrode,whereby the dia-meter of said arc at arcing surface is substantiallylarger than the diameter of said arc at a region between said annularwall and said electrode, said annular wall being sufficiently large indiameter to permit transmission of light from a point lying on said axisand also on said arcing surface and in a direction having a substantialcomponent radial to said axis, said light passing through saidtransparent wall means to the exterior of said apparatus.

10. The invention as claimed in claim 9, in which outlet means comprisesa plurality of passages the intake portions of which are disposed atleast as far from said axis as is the portion of said annular wall whichis nearest said axis.

11. Apparatus for generating high-intensity light, which comprises:

light-transmissive wall means including a surface of revolution about acentral axis,

said Wall means defining an arc chamber, a metal electrode having arecess therein, means to pass coolant through said electrode to effectcooling of the side and bottom walls of said recess, means to maintainan electric arc in said chamber between said bottom wall and a secondelectrode which is spaced and insulated from said metal electrode,

said arc extending along said axis of said surface of revolution, meansto continuously introduce high-pressure gas into said chamber and toeffect vortical flow of said gas around said axis and thence into saidrecess, and means to continuously drain said gas from said recess forgenerating high-intensity light,

through outlet means located adjacent the peripheral portion thereof.

12. The invention as claimed in claim 11, in which said side wall ofsaid recess is annular and is coaxial with said axis.

13. Apparatus for generating high-intensity light, which comprises:

light-transmissive wall means to define a chamber a wall of which is asurface of revolution about a central axis,

first and second metal electrodes having end portions disposed in saidchamber at spaced points along said central axis,

the end portion of said first electrode having a recess formed therein,

the side wall of said recess being annular and coaxial of said axis,

the bottom wall of said recess being substantially solid and 4beinggenerally transverse to said axis,

means to effect continuous introduction of high-pressure gas into saidchamber,

said means being so directed as to eect flow of gas vortically in saidchamber about said axis,

means to effect continuous discharge of at least a major portion of saidgas from said chamber through outlet-opening means the intake portion ofwhich communicates with said recess adjacent said side wall thereof,

a D C. current source having the positive terminal thereof connected tosaid first electrode and the nega-tive terminal thereof connected tosaid second electrode,

said source being adapted to maintain a high-current electric arc alongsaid axis between said second electrode and said bottom wall of saidrecess,

the light generated by said arc being transmitted through saidlight-transmissive wall means.

14. The invention as claimed in claim 13, in which said current sourceand said gas-introduction means are so correlated to the diameter ofsaid recess side wall that the portion of said arc in said chamber has adiameter substantially smaller than the diameter of the portion of saidrecess side wall closest to said second electrode.

15. The invention as claimed in claim 13, in which said end portion ofsaid second electrode is free of substantial gas outlet openings at saidaxis.

16. A high-intensity radiation source including an anode elementeffecting a heat-sink and pressure-sink operation, which comprises:

wall means to define an arc chamber,

said wall means including a transparent portion to transmit light out ofsaid chamber,

anode and cathode elements disposed in said chamber to maintain an arctherein,

said anode element comprising a hollow metal body having a recess in thesurface thereof,

said recess having a bottom wall adapted to provide an arcing surface,said recess having a side wall at least a portion of which is a surfaceof revolution about a central axis, said hollow body also having are-entrant portion opposite said recess,

said re-entrant portion having water passages therethrough extendingfrom the end of said re-entrant portion to the vicinity of said bottomwall of said recess and thence extending radially-outwardly to theperiphery of said re-entrant portion,

a water-separator tube extending into said hollow body and around saidre-entrant portion in radially spaced relationship therefrom,

means to introduce water to the interior of said water 13 separatorwhereby to eifect flow of Water through said water passages in saidre-entrant portion and also to eifect ow of Water through the gapbetween the periphery of said re-entrant portion and said waterseparator,

means to discharge water from the space surrounding said Waterseparator,

a D.C. power source having the positive terminal thereof connected tosaid anode and the negative terminal thereof connected to said cathode,

means to introduce gas into said arc chamber, and

means to discharge gas from said chamber through said recess and throughgas passages formed in said reentrant portion,

said gas passages communicating with said recess adjacent said side Wallthereof.

17. The invention as claimed in claim 16, in which References CitedUNITED STATES PATENTS 11/1962 Gage 315-111 X 6/1966 Miller 313-231 XJAMES W. LAWRENCE, Primary Examiner R. F. HOSSFELD, Assistant ExaminerU.S. C1. X.R. S13-30, 231

